I prefer to hybridize my characters by finding ways to let a focused character deal with the other armor type... or bypass it.
For example: Warrior types can invest a point into polymorph and take bull rush. Now you have a spammable "bypass armor" that you can use to help your mages out.
All of my casters like one or two points into necromancer for locust swarm and decaying touch to help the physical guys out.
If I chose wand + shield, I find it worth investing a point into warfare later game for shield lob.
Archers, of course, have the piercing shot.
